1. Field of the Invention
The invention relates to a heat-insulating body having a particulate insulating material and a sheath of a sheet material, which is made by filling the sheath with the insulating material and subsequently shaping the sheath filled with the insulating material and compacing the insulating material, by applying excess pressure to the outside of the filled sheath.
2. Description of the Prior Art
DE-PS No. 1,954,992 discloses heat-insulating slabs which include a core of a mixture of finely dispersed materials, for example expanded silica, opacifying agent and mineral fibres, and an outer sheath of glass fibre fabric or the like. To make such slabs, generally the mixture of the finely dispersed materials is introduced into a sheath of glass fibre fabric or the like. Thereafter, the sheath is sewn up and pressed in a pressing operating to form a slab whose size depends on the dimensions of the sheath.
According to DE-PS No. 2,036,124 the pressing operation is carried out so that an intimate as possible interengaging of the finely dispersed materials together and with the surface or pores of the relatively rough sack material takes place so that upon completion of the pressing operation a sandwich is usually obtained. This sandwich includes the core of finely dispersed materials and the sheath. If the surface of the sheath is very rough or porous, without taking special steps, however, it is inevitable, or intended according to DE-PS No. 2,036,124, that the core material penetrates at least partially into the pores and thus anchors the core to the surface of the sheath. Such slabs have a relatively high bending stiffness and when subjected to bending stress break practically without appreciable deformation. Such insulating slabs are thus unable to adapt themselves to the irregularities of the object to be insulated, i.e. it is not readily possible to apply such slabs to surfaces curved in one or two dimensions.
A further disadvantage resides in the fact that the pressing operation for making such insulating slabs must take place relatively slowly. When the pressing operation is carried out relatively rapidly the cores of insulating slabs made in this manner have a slate-like inhomogeneous structure so that due to the resulting irregularities, the coefficient of the thermal conductivity of these slabs is impaired compared with a homogeneously pressed slab. In addition, insulating slabs made by such a method tend after pressing, due to the slate-like structure, to spring back to a relatively pronounced degree so that the thickness differences from slab to slab are relatively great.